The investigation of the penetrating radiation has followed a peculiar course in this that the most different properties of the radiation, its intensity distribution, absorption, scattering and even its origin have been examined and discussed, while the really fundamental question of its nature has hitherto found no experimental answer. If hitherto by common agreement preference has been given to the view that the penetrating radiation is a very hard y-radiation, this came to pass solely on account of its enormous penetrating power which only with greater difficulty could be thought to be associated with a corporeal radiation.
Always the fundamental possibility of electron radiation has been pointed out by nearly all the authors concerned."
Such a stream of electrons has been sought by Schweidler, Swann and Hoffmann in order to explain the maintenance of the negative charge of the earth. They endeavored to find an accumulation of electric charge on an insulated metallic conductor as an effect of the hypothetical stream of electrons, but their results were negative.
On the other hand, Skobelzyn, using C. T. R. Wilson's cloud apparatus has demonstrated the presence of electrons moving with high speed and not of radioactive origin.
In order to investigate the nature of the penetrating radiation Geiger and Mtiller's tubes for counting electrons were used. Two tubes with their axes parallel were placed a few centimeters apart. The arrival of an electron in each tube caused a deflection of the attached electrometer.
The deflections due to both tubes were registered on the.same film. Altogether about go,000 such deflections were recorded.
When deflections were registered at the same instant from both tubes this coincidence was interpreted to mean that the same particle had traversed both tubes. Experiments were conducted both in the basement and in the attic of the main building of the Reichsanstalt in Charlottenburg.
As an example, one series in the basement lasted 15 minutes. On the 823 cm. of film used there were 619 deflections due to the upper tube and 364 to the lower, which was vertically beneath the other. Of these 33 coincided in time of occurrence.
The number of accidental coincidences was calculated to be 5.5. This leaves 27.5 actual coincidences.
When a block of gold was placed between the two tubes 531